#include <iostream>

int main() {
    int score;
    std::cout << "Please enter score (0-100): ";
    std::cin >> score;

    // if-else示例
    if (score >= 90) {
        std::cout << "Excellent" << std::endl;
    } else if (score >= 80) {
        std::cout << "Good" << std::endl;
    } else if (score >= 60) {
        std::cout << "Pass" << std::endl;
    } else {
        std::cout << "Fail" << std::endl;
    }

    // switch示例
    switch (score / 10) {
        case 10:
        case 9:
            std::cout << "A" << std::endl;
            break;
        case 8:
            std::cout << "B" << std::endl;
            break;
        case 7:
            std::cout << "C" << std::endl;
            break;
        case 6:
            std::cout << "D" << std::endl;
            break;
        default:
            std::cout << "F" << std::endl;
    }

    // for循环示例
    std::cout << "\nUsing for loop to print 1-5: ";
    for (int i = 1; i <= 5; i++) {
        std::cout << i << " ";
    }

    // while循环示例
    std::cout << "\nUsing while loop to print 5-1: ";
    int num = 5;
    while (num > 0) {
        std::cout << num << " ";
        num--;
    }

    return 0;
}